1. Field of the Invention
The present invention relates to an ink stock solution and an ink composition.
2. Background Art
With the spread of the computer in recent years, ink jet printers are widely used not only in offices but also in homes for printing on papers, films, cloths, etc.
As ink jet recording methods, a method of ejecting ink droplets by applying pressure by piezo-elements, a method of ejecting ink droplets by generating bubbles in ink composition by heat, a method of using ultrasonic waves, and a method of suction-ejecting ink droplets by electrostatic force. As the ink compositions for these ink jet recording methods, an aqueous ink, an oil ink composition and a solid ink composition (a melting type) are used. Of these ink compositions, aqueous ink composition is mainly used for easiness of manufacture and handling, odor and safety.
Colorants used in these ink compositions for ink jet recording are required to have high solubility in a solvent, to be capable of high density recording, to be good in hue, to be excellent in fastness to light, heat, air, ozone, water and chemicals, to have good fixing property to an image-receiving material and to hardly blot, to be excellent in preservation stability as ink composition, to be free of toxicity, to be high in purity, and to be available inexpensively. However, it is extremely difficult to search for colorants that satisfy these requirements on a high level.
Various dyes and pigments have been already proposed for ink jet recording and practically used but colorants that satisfy all of these requirements have not been discovered yet. It is difficult for dyes and pigments having Color Index Nos. (C.I.) to reconcile the hue and the fastness required of the ink compositions for ink jet recording.
The present inventors have proposed cyan dyes having excellent hue and fastness (refer to, e.g., JP-A-2003-321630 (The term “JP-A” as used herein refers to an “unexamined published Japanese patent application”.) and JP-A-2004-75825).
In manufacturing an ink composition, e.g., an ink composition for ink jet recording, powders of dyes are generally used, but it is advantageous to manufacture an ink composition from a concentrated ink composition, that is, an ink stock solution considering handling property and solubility.
However, when a dye having a high oxidation potential is used in an ink stock solution for ink jet recording that is the feedstock of the ink composition for ink jet recording, the viscosity becomes extremely high, so that serious problems arise in handling properties at the time of feeding and filtering of the ink composition.